K. van Salis & A. lnnnenh au ser: Mesozoic Nannofossils from Oman .... , p. 95-101.

Journal of Nannoplankton Research. 19. 2. I 997.

MESOZOIC CALCAREOUS NANNOFOSSILS FROM MASIRAH
ISLAND (SULTANATE OF OMAN)
Katharina von Salis, Geologisches Institut ETHZ, CH-8092 Zurich, Switzerland & Adrian Immenhnuser.
Mineralogisch-Petrographisches lnstitut der Universitat Bern, Baltzerstrasse I, C!l-3012 Bern, Switzerland.
Present address: l rije Universiteit, Faculty of Earth Sciences, De Boelelaan I 085, NL-I 081 Hi/Amsterdam, The
Netherlands

Ahstrnct:Calcarcous nannofossils were studied in support or the geological mapping and structuralinterpretation or Masi rah Island in Oman. The assemblages found include Middle Tr iassicr"),
Early Jurassic (Late Plicnsbachia n), and Early as well as Late Cretaceous assemblages from aiinle-known region between the western Tethys and the Pacific Realm,

Introduction
Masirah Island is one oft he less well-known fragments ofocean floor occurring at the southeastern coast of Oman
(Figure I). The island extends over roughly 700km' and isformed by two well-exposed ophiolite nappes (Marquer etal., 1995) presently under study by a group of earthscientists at the University of Berne and Neuchatel (Peters et al., I 995).

crust oft he evolving proio-lndian Ocean which opened in
the Late Jurassic between West and East Gondwanaland(e.g Salman & Abdulah, 1995). Masirah became part of
the northward drifting Indian Transit Plate (including Pakistan and the Seychelles), when this plate separated fromAfrica/Madagascar after 84Ma (lmmenhauser et al .. I 997).
The ophiolite was obducted in its present position onto
the continental margin of SE Arabia at Crctaceous/Terti-

ary boundary times, around 65Ma. The
abduction is tJ1ought to be related to oblique.
hot-spot (Deccan Traps)-induced rifting between India/Pakistan and the Seychelles
Microcontinent at 65Ma (Plummer & Belle,
1995: Immenhauser et al.. I 997).
The autochthonous sedimentary
cover
oft
he lower of the two ophiolite nappes
J.,JC Conladan-Santonlo
I-2!6C Coniudan/SantonJan-Lower C•mpanlaaonMasirahprovides an unbroken
I-257C CooJadan/San1ooku1
1-l60C Conlulflo/Santonlan-SaMOJ'tlan
stratigraphic record from 150Ma to 65Mal•l61C CouLaclao/Sanlonbl.a.
1-:2$1C Conladao/Santoalan•U>lffr c.u.paalan(lmmenhauscr. 1995). The elating of samples
f-'2$2C Conlaclan/Santonlan.-Lowu Campanian
Wadi Al Ftray
I-74.2C Alblanof the highly tectonised sediments was
WacllSbJtln:dI-87C Valanglnlan-Apclan
achieved by calcareous nannofossils,
1-259C Tu roo ian
Wadi Al Flra )'WadtSbl'lmi
1-357.lC Campanb.n
foraminifera and radiolaria (Dumitrica et al.,We11ttrn End or Wadi Al TI.ray -fr,f.--"~.,.JlijEfffll.--1997). Much to the surprise of the authors,also the Middle Triassic yielded question1-334.lC Berrlaslan
able calcareous nannofossils. and Lower
J-356 C Uppermost Ma•tncbUA.D.
Sur Ma.lnh {Coast)
Wadi Al Fln.y
Re"'l'forked In TertMlry
Jurassic calcareous nannofossil assemblages
sattdttota?
were found besides the expected Lower andI-319C Tttbonian,BerdMlan
WadlTboumlUpper Cretaceous ones. Since the knowledge
about Triassic and Lower Jurassic calcare1-llOC Tltbon.lan-Lowc.r Aptlan
ous nannofossils from the southeastern part
Wadi Mag.blahof the Tethys is small, we decided to present
1-lllC &n-lMl.lln-HautcrMan
LogXXI
the new findings in order to complement thel-31~ Beniaslan/Valangtnlag
I..JJOC Burlado.n-Haukrtvloa
present palaeogeographic distribution picI-331C &rrlMiao·Valangilllan
l-332C ~rrtasln-VaJahgln.lan
1-334C 8err1Mlan/Val.a.nglnlan-Hau11ertvlao
ture.
I-596C AlblanSince reports about calcareousl-643C Ca m pu lanWadl Haql
Fayah Unit
Maa.!ltrkbtla.nnannofossils from other time periods of this
1-$1! Conl&da n/S•ntoolan boundary
1-231C Alblan[illil Kalban Unit
Wlldl Qu.Uaor
part of the "vorld are scarce too, we also
J.ti3.1R Aptlaa ce Lowee Alblan
1-637R !1-,Jd-Upper Alblan
present the results of the nannofossil analyNortb or Suwayr~ Maghllah Unit
1-290C A.tblan/Ccoomanlanses from later time periods and discuss theS. or Jabel Suwayr
problems encountered in the age assignment
Figure t: Map of Masirah Island, Sultanate of Oman. showing the localities yielding of the various sediment packages.

MASIRAH ISLANDmuseful calcareous nannofossil assemblages.

Material and methods

The Masirah Ophiolite was formed about l 50Ma
(Figure 2) during the Late Jurassic/Early Cretaceous at alatitude of38°±12°S (Gnos & Perrin. 1996; lmmenhauser,
1995, I 996). It belongs to the oldest-preserved oceanic

Spot-samples for age determination by coccoliths werecollected from pelagic sediments and were mainly taken in
the shaley partings and interbeds of radiolarian micrites

95Journal of Nannoplankton Research, 19, 2, 1997.

K. von Salis & 11. Immenhouser: Mesozoic Nannofossils from Oman ..... p. 95-101.
Figure 3: Distribution of Upper Pliensbachiancalcareous nannofossils from Masirah Island

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Figure 2: Palaeotcctonic map of the Toarcian, modified alter Ricou(1994), with position of Masirah Island and Lowa Jurassic calcareous
nannofossil occurrences after de Kaencl & Bergen (1993). Bown (1987).
Erba et al. ( 1992) and Kristan-Tollmann ( 1988). Triassic occurrence
all er Bralower et al. ( I 991 ).

and even from ribbon-bedded cherts. Upper Cretaceous
flysch-type sediments were best dated with samples taken
in shalcy interbeds. Simple smear-slides were prepared fromthe samples and embedded in Canada balsam. The study
was undertaken at a magnification of x I 000 with a lightmicroscope (LM) equipped with polarisers and a gypsum
plate. Approximately 250 smear-slides were prepared ofwhich some 20% yielded more or less datable coccolith
floras. A few samples were also studied by scanning electron microscope (SEM). the preparation following the usualtechniques as described in Perch-Nielsen ( 1985).

Middle Triassic
Sample I-620, which yielded Middle Triassic radiolaria also
included forms which - with doubt - may possibly be assigned to the calcareous nannofossil genus Calyculus.
This genus was described by Noel ( 1973) from the Toarcian(Lower Jurassic) of France and consists of subvertical elements surrounding a relatively wide central area. According to Erba et al. (1992), "Calyculus has not been reported
from older than Toarcian sediments so far". While the organic origin of the specimens illustrated in Plate I. Figures
1-3 seems likely. their generic assignment must remain
speculative. No other calcareous nannofossils were foundby SEM nor LM in sample 1-620, which yielded the following age-indicative radiolaria: Tritortis balatonica
Kozur and Tritortis kretaensis subcvlindrica Kozur (Upper Langobardian or Lower Cordcvolian; Dumitrica el al.,1997).

Lower Jurassic
The age assignment of Early Jurassic was essential in proving the presence of exotic sediment blocks older than theformational age of the ophiolite on which they were found.
Exotic sediment blocks on Masirah Island form part of
the Upper Cretaceous Fayah Unit and were shed in thelatest Maastrichtian (see below).
Three samples (I-240, 1-243 and I-244: Figure 3)
were found to include the very rare to rare. poorly to moderately well-preserved calcareous nannofossils listed in Fi
gure 4. Sample I-243 was only studied by SEM. The illustrations are shown on Plate I. The fact that the assemblages are different is probably due to the dilTcrent technique used for their study in the case ofl-240 and I-243,
and by the very poor state of preservation of the coccoliths

240 R p +243 vR p +244 vR vP +

I

(/)

(I)

U)

(/)

(/)

C:

..Q

..Q

+ + + + + + + + + + +
+

(/)

(I)

(/)

U)

(/)

(/)

(/)

C:

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(/)
C:

C:

C:

U)

(/)

+ +

+

+

+

+

in sample l-244. For LM illustrations sec Crux (1987) andde Kaenel & Bergen (1993), who also present SEM pictures.

Age
Only sample 1-240 can be used for an age determination.
The presence of Lotharingius sp., the first. small form ofthat genus, suggests an age not older than late Early
Pliensbachian (davoei Zone of Northern Europe and Portugal. according to de Kacncl et al. (1996)). The presenceof Biscutum profundum means, however, that the sample
is of even younger, Late Plicnsbachian age (margaritus
Zone). At the same time. the sample cannot be younger.
since it includes Parhab dotithus rob us/us, the last occurrence (LO) of which has been reported in the same zone byde Kaenel et al. (I 996 ). This age assignment is contradicted by the distributions reported by Bown ( 1996) who
reported the LO of P robustus in the Lower Plicnsbachianibex Zone.
Palaeogeography
The assemblage in sample 1-240 is as rich as coeval assemblages from the western and eastern Tethys or from
Northern Europe, and no forms restricted to Oman were
found. From the palaeogeographic map (Figure 2), it follows that the Lower Jurassic coccolith assemblage reported
here was deposited about mid-way between the ItalianJurassic assemblages which were classified as 'tethyan'
and those labelled 'pacific' in Timorby Bown ( 1987). While
one Masirah assemblage includes Mitrolithus jansae,
which was found by Bown ( 1987) to be restricted to an
equatorial/sub-equatorial belt and absent in the Pacificsamples from Argentina and the Queen Charlotte Islands(Bown, 1992), none includes Mazaganella pu//a or
Mazaganella protensa that were reported by the sameauthor from the southern edge of the Tethys. The sample
also lacks Crucirhabdul us primulus and Parhabdolithus
liaslcus, two species usually found in Plicnsbachian assemblages.

Cretaceous
A synthetic composite section of the autochthonous Cretaceous sediments on the lower nappe of the Masirah
Ophiolite, as reconstructed from observations in the field
and the ages derived from coccolith, foraminiferal andradiolarian dating, can be found in Immenhauser (1995).

96

K. von Salis & A. lmmenhauser: Mesozoic Nannofossils from Oman .... , p. 95-101.

Journal of Nannoplankton Research, 19, 2, 1997.

-..JI\.)I\.) I\.)w WW WWSAMPLEw
w C,.) I\.) ~~ CD CD -..JI\.) <D CD .I>, .I>,I\.)~ 0 <D <D 0 ~o .I>,~ (Jl -..J f\.) ~-..J< <'Tl :n :n :n :ii + + + :n + + :n :n + :n + ;!;! + + :n + + + :n :n :n :n ~ABUNDANCE
0,

w w w

C,.)
(Jl (Jl (Jl (Jl (Jl (Jl (JlCJ)(Jl .I>, .I>, ~ (Jl .I>,..,. WW(Jl -..J 0, (,J ~ 0, I\.) ~ (Jl .I>, .I>, (Jl .I>,
0,

WO <D <D

< < < < < <-0 -0 PRESERVATION-0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0
3-0 -0 -0 -0 ~ -0 -0 -0< <Assipetra infracretacea
Biscutum sp.
+
Braarudosphaera sp.
++
Calcica/athina oblongata
.-,
.
. -,
Crepidolithus sp.
. -,
. ..,
.
..,
+
.-,
Cruciellipsis cuvillieri
+
+
+
+
+
Cyc/age/osphaera margerelii++ + +Cyc/agelosphaera deflandrei++ + + + + +Cyc/agelosphaera sp.
++ ++Diazomatolithus
lehmannii
+
+
+
+
+
+ +
Discorhabdus sp.
+•..,) ·..J
Eiffellithus windii+ Ellipsage/osphaera frequens
Ellipsage/osphaera sp.
+
+
+ +
+
+
+
+
+ + + Eprolithus flora/is+
Eprolithus sp.
. .., +
+
+
+ +
+
.-,
Glaukolithus diplogrammus+
Haqius circumradiatus+
Hexalithus hexalithus+
Kokia? sp .
. -,++ Lithraphidites carniolensis+ ++ + + ++++)> "(J 0-....) -...,).-, Lithraphidites morayfirthensis
r11 11i] 0Loxolithus sp.
++~-~~+ + + + Manivitella sp.
_:, II g
Micrantholithus sp.
+:,.3:,:,'08_ II.-,. ....:, •...,) Microstaurus chiastius
II (t) (D
+
+
+ .-,
+
. ..,
Nannoconus globulus~~-~+ti>·_rn :n
p < II
Nannoconus steinmannii++
00 II siJ
Nannoconus (top-views)
m~@
+
+
+
II-< ..
CD+. +.-,
Nannoconus sp.
+
+
3.t-&
lb C Cb
Palaeomicu/a maltica
+
f!2.g
~
O>n,:,
Pa/aeomicula variabilis+ + +:, ;:i Podorhabdus sp.
s·
+
"
.D
.
.
Po/ycostella beckmannii
C(1>
Polycostella senaria
5'1+gPolycostella sp.
:n
+
+ + +
"tr
Prediscosphaera columnata+
Prediscosphaera sp.
+
Ouadrum ? sp.
++ +Reinhardtites cf. R. anthophorus+
Rhagodiscus cf. R. asper+. ._, Rucinolithus hayi
+ Rucinolithus irregularis+ ++Rucinolitlws wisei
+
+
+
+
,..,
Rucinolithus sp.
++++
Stradneria crenulata
+ + +
+ +
+
+ +
+
+ + +
+
+
.
Triquetrorhabdu/us ? shetlandensis
Tubodiscus jurape/agicus+,1 Watznaueria barnesae'Tl + + + + + + + + + + :n :n :n ,:n + :n + + :n + + + :n :n JJ JJ+ Zeugrhabdotus embergeri++ + + + + +
+ +
+ +
+
+ + +
,..,
Zeuarabdotus erectus
Zeugrhabdotus sp.
+ +
.-,

+

+

·-V ·"V

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~ I\.)I I\.)I I I I\.)"r ')' .~1.., -..J .....,.-, J..
.I>,

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J> CD J> )> J>-0 -0 -0rm·'V •...,) ·..J . ...,:, •--.)-..J -..J CD.-., . .., lll.-,-..iCCZONES
er Sissingh (1977))> J> )> )>-0 -0 -0 "O STAGE. ......,...,

coccoliths. Their distribution in some samples is presented
in Figure 4. The age assignment of many samples wasdifficult and often represents an educated guess rather
than a firm statement. Nevertheless, the presence offonns
generally used for the biostratigraphic subdivision of theLower Cretaceous of the Tethyan Realm allows for an approximate age determination of a dozen or so samples. The
knowledge of the presence of these species in this part ofFour groups of Cretaceous assemblages could easily be distinguished on the basis of their calcareous
nannofossil content (Figures 4, 5). They are dated, where
possible, according to the zonation proposed by Sissingh( l 977), taking into account also the findings of PerchNielsen ( l 985) and Bralowcr et al. ( 1989).
The sediments that were assigned an Early Cretaceous age include only poorly- to very poorly-preserved

97Journal of Nannoplankton Research. 19, 2, 1997.

K. von Salis & A. lmmenhauser: Mesozoic Nannofossils from Oman ... , p. 95-101.

the Tethys may prove useful in future studies. Classical markers used in the Tethyan Realm for zonation
found herein are: Calcicalathina sp. (?). Crucietlipsis
cuvillieri, Eprolithusfloralis, Microstaurus chiastius,
Po/ycostel/a beckmannii, P senariat'Iv, Prediscosphaera colunmata, Rucinolithus irregularis andvarious species of Nannoconus. Forms known mainly
from the Boreal Realm include Kokia sp.t") andl.ith raph t dite s mor avfi rthen sist'tv. The poor
preservation does not allow for an unequivocal determination of the forms indicated by'(?)'.
Three major Upper Cretaceous assemblages
were found (Figure 5): the Coniacian/Santonian is characterised by the presence of Marthasterites furcatus(which, however, ranges from the Late Turonian
through the earliest Carnpanian. but is most common in
the Coniacian and Santonian), The Carnpanian isapproximated by the presence of Broinsonia parca
parca and the Upper Maastrichtian by the presence ofMicula murus, the marker-species for the uppermost
Maastrichtian. Other Upper Cretaceous marker-species
include Arkh angelskiella cymbiformis, Eiffellithus
eximius, Helicolithus trabeculatus, Lithastrinus
septenarius, Lithraphidites quadratus, Prediscosphaera stoveri, Reinh ardtites anthophoru s andTranolithus orionatus.
Upper Cretaceous sediments from Oman were
the object of a special study on the evolutionary trends
in the family Arkhangelskiellaccae by Lauer (1974). In
our material, specimens of this family were not common and thus were not restudied especially, An intensive search in the field for samples above those that
include Micula murus, in order to find sediments including Mi cu/a prinsii, the marker of the terminal Cretaceous, or even a Cretaceous/Tertiary boundary sect ion, was not successful. The contact with these dirnents overlying those including M. murus is
tectonic.

"'"' "'"'

~"'

:n 0

'O 'O ~ 'O ;;: 'O ;;:;;: 'O ;;: ~ 'O
uu 3u

+
+

I

Systematic remarks
Systematic information and illustrations of the calcareous nannofossil species listed, mentioned and illustrated can be found in Perch-Nielsen (I 985), Bown
( 1987) and de Kaencl & Bergen ( 1993 ).
Discussion and conclusion
What had started out as a routine biostratigraphic investigation of samples collected by a geologist in the field inorder to help him with the interpretation of the complicated geology, turned out to actually change the previous'ii 'O <;;:
'Ou 'i, PRESERVATION'Nkhange1 d<ieila sped/Iara
IAssipara inlracr etacea (RW)SiSCl.llum sp_
Braarvdosphaera bi"'"',..,·"'
Brdnsonia enorm is
Broiw
JOniaparca s.a
Bukrvlilhus ambiows

._,

+ +

+

+

"

+

+

+
+

+

+

+
+

+

.,., ++ +I +
+ + +
+

+

+

Chiastarvau s am"";~+ Chiasto711aus fessus+

Ccnusphi, •ra sp. (RW>Cor o/Nrhion ? mada.Qaskdrensis
Cacllilhion s;g,.,m
CrepkJolithus ? sp.

+

+ + +

+ +

+

+ +
+
+ +

+
+

Cerarolilhoides acvl oos

+

+
+
+

"

Cr Btarha bdu s c:a,icus

+

+

+

:n

+

Cribrosphaerella ehrenbergii
Cr uciellipsis C'U\fHi«; ( RW)!r.vrlaqeJesphaera de/Jandreif":vc/aqeJcsphaera matfU!111'e/lii

+

+

+

~indralithi.Js ~ Diazom ato/ithus lehm annii (RWJ

+

+

+

+ + + + +
+ +
+
+
+
+ + +

+

+

+ ,._,, £jlfeJJithus eximius

+

+ + +

+

Eiffellithus paraflf!lu s.,., + + + + Blfeltirhus turriseiffel#
Eilfellithus sp,
Blipsoli rhus comm unis (RW)+

IED rclithus fkxafis

+
+

+
+ +

+

+

.,.,

.,.,

Gartnerago obliquum+++

Glauk o/ithus compa ctus+

Glauk olithus dip logramm us

Grant.arhabdus ccronadventis
Helicolithustrilbewlatus
Holoooccolilh
Kamotnerius ma,.,.,;,;cvs++ .,.,+++

Uthastrinusan·1»

+
+
+

+
+

+

+ +

Litha strinus sep tena rius+

Lithastrinus 9'>
Uthraph; dit es qua dratus

+
+

+ +

+
+

+

Uthraphi diu,s "' ·Loxdithus $p.

+

Lua "anorha bd us ~ -

+ +

+ +
+ +
+
+

+

+ + +

+

+ +

lv1anMtella MYnmatoidoo
Ma rtha stwires flxca tus

Maantholithus obtusus (RW)+

Maorha bduJus atten uaws++
+ ._, + + + + ++M actha bduJu s decor atus
Mcr aha bdulus undosv s++ + + +

+ Mcula decu ssa ta
Afcula m i.vus++

Mcul a praem i.vus+

Nfcul a SW1stica

+

+
+

+

+

+

Ni3nnoccnus sp. (AW?)
Petrarh afxlus cop ula tus+ ++++ + + +
+

.,.,
+

+ +
+ + +
+
+

Pla,.,, ,......, ,s fibulffo,m is+

PfJcozygu s cl. P sigmai desPrediscosp ha 8fa a«aooa+:n + Pr ediscosp ha «a ~ .

+ + +co·"Tl
C

...

(1)
(11

..

-s....

CJ

iii'

0-

o·

::::,

0

C
-0

...
0
...

~

!1
II)
0

~

C
Ill
0
Ill

0

...

Ill
(1)

0

C
Ill
::::,
Ill

::::,

::::,

0
0

Ill

-

!!!.

U)

...
0

3

:ii:
II)

Ill

::;·
II)

=sU)

iii"

::::,

a.
:il

g
II

m

~
~

Prediscospha er a spino sa
Prediscospha er a stoveri+

Prolatipa tel/a mu/ tica rina ta
Qua dru m aarrneri

+ + +
+

+
+

+ + + Oua drum sp. 1
Ouadrum sp.2+
RtJW>a rdtitet; mirabilis+
Reinha rdtitet; anthoph au s
+

+

.,.,

+

.,.,

Rhaaodiscus asp er (AW)++Rhaaodiscus eJon ga tu s
Rhaaodi scus reniform is+

Pthaaodiscu s sp/ enden s
Rorelapi/ Jus munitus++ + + + + +
+
+
+
+

+

"'

IArkha ngel skiel/a cvm bifamis+

Tertiary
Very rare Tertiary coccoliths were found in several samples. They include Coccolithus pelagicus and small
Prinsiaceae, such as are found from the Paleocene
through the Recent, and Chiasmolith us solitus(Eocene). It has not been possible to ascertain thatthese occurrences are actually dating the sample inquestion. Since many samples included no coccoliths
at all, contamination in the laboratory seems, however,unlikely.

"'"'"'... "'<D

m<1> (}> (,) (,) (,) 0, a,... <D<1'0~SAMPLEen '-" tr1~(,) (,) -,J-,J mm ~o <D __, ourc ~ <D "'(,)
'Tl
<
'Tl
+ + 'Tl+ f;? + QQ <:n ABUNDANCE:n 0 'ii :n :n :n++++ St radner ia a enula ra
Tea umen rum str adn eri (AW)
Tetrannnnrn:. bdu s deccf us
Tn a acospha era ~

+

+

+ +
+ +

+

"

Rucino/ ithus ~So/Jasites sp.

++ + + ++

Trano/ithu s ga ba lus++

Trandithu s minim us+ + Trandirhus Dh acelosu sla iona tus
Un iplana rius aahicus+

Uniplanarius trifidu s;ii + JJ :n 'Tl :n :n :n

+ + +
+

+

+

+

+

+

+

+

+

+ +

~ :n Warmaueria barnesa~+

eugrha bdctv sem bergtJf ;Zeu grha bdotu s «ecrus

.,.,

+

zeu ~ bdotu s pseuda ntfqih oru s,_,~'f~ ;:;! .,.,. ...,~ t CC ZONES"''ftt "'"'
-,:
'f
i~
<»
! m "'"' "'"'
;;:,
"'
mo
._.,-.J"'(,).., i::l Slsslngh (1977)I

Q (,)•-.) •-.)-,J

I"'"' .

I\)·-.) ·-.)"

geological picture considerably. In addition, it provided aninteresting surprise in the fonn of enigmatic Middle Triassic
nannofossils and an Early Jurassic calcareous nannofossil
assemblage from an area from which none was previously
described. This assemblage could be shown to correspondbroadly to those found in the western part of the Tethys.

98K. von Salis & A. lmmenhuuser: Mesozoic Nannofossils from Oman ... , p. 95-101.

According lo Bown ( 1987), the relatively common presenceof Calcivascularis jansae "reveals the tcthyan affinities
of a nannofossil assemblage immediately", At the sametime, it seems that some of the species usually present in
the tcthyan Pliensbachian. such as Crucirhabdus primulus
and Parhobdolithus liasicus. arc missing in the samples
studied.
The often relatively poor slate of preservation of
the Lower Cretaceous calcareous nannofossil assemblages prevented the assignment of most samples to a
specific zone. Nevertheless, a more broad age assignment
was possible in many cases and sometimes supported byradiolarian stratigraphy. Also, the Upper Cretaceous assemblages were rarely well enough preserved to allow fora clear zonal assignment.
Acknowledgements
This research was supported by the Swiss National Science Foundation (project No. 22-33559.92). Work on
Masirah Island was possible due to the help oft he Ministry of Petroleum and Minerals of Oman. especially Mohammed Bin Hussein Bin Kassim, Director General of Minerals, and Dr. Hila! Al Azri, Director of the Geological
Surveys, who provided logistical help and support. Dr. E.
de Kaenel (Neuchatel) verified the determinations of theJurassic coccoliths. F. Zweili provided valuable technicalhelp with the SEM. Dr. J.A. Burnell and Dr. P.R. Bown
reviewed the manuscript.
References
Bown. P.R. 1987. Taxonomy. evolution. and biostratigraphyof Late Triassic-Early Jurassic calcareous nannofossils
Special Papers in Palaeontology. 18: 1-118.
Bown. P.R. 1992. Late Triassic-Early Jurassic calcareous
nannofossj ls of the Queen Charlotte Islands. l3ritish
Columbia. Journal ofA licropnlneo11rolof.;_1', 11 (2): 177-188.
Down, P.R. 1996. Recent advances in Jurassic calcareous
nannofossil research. In: A.C. Riccardi (Ed.), Advancesin Jurassic Research. Geollesearch Forum. l-2: 55-66.
Bralowcr, T.J., Bown, P.R. & Siesscr, WC,. 1991. Significanceof Upper Triassic nannofossils from the Southernl Iern isphere (ODP Leg 122. Wombat Plateau, N.W.
Australia). Marine Micropaleontologv, 17: 119-154.
Bralower, T.J., Moncchi, S. & Thierstcin. 1-1.R. 1989. Calcareous Nannofossil Zonation of the Jurassic-Cretaceous
Boundary Interval and Correlation with the Geomagnetic
Polarity Timescale. Marine Micropaleontology, 14: 153-235.
Crux, J.A. 1987. Early Jurassic calcareous nannofossil
biostratigraphie events. Newsletters 011 Straugraphy. 17(2):79-100.
Dumitrica, P., lmmenhauscr. A. & Dumitrica-Jud , R. 1997.
Mesozoic radiolarian biostratigraphy from the Masirah
Ophiolitc (Sultanate of Oman). Part I: Middle Triassic, Uppermost Jurassic and Lower Cretaceous Spumellarians andmultisegmented Nassellarians. Bulletin of 1/,e National A-111scum of Natural Science. Taichung, Taiwan, 9: 1-106.
Erba, E., Castradori, D. & Cobianchi. M. I 992. Compilation

Journal of Nannoplankton Research, 19. 2, 1997.

of Upper Triassic and Jurassic calcareous nannofossil
ranges. In: F Proto Decima. S Moncchi & D. Rio (Eds).
Proceedings of tire !NA Conference. Firenze. Memorie di
Scienze Geologic/re. -t3: 27-40.
Gnos, E. & Perrin, M. I 996. formation and evolution of theMasirah Ophiolitc constrained by paleomagnetic study of
volcanic rocks. '[ectonophysics, 253: 53-64.
lrnmenhauscr. /\. 1995. The autochthonous Mesozoic sedimentrecord on the Masirah Island ophiolitc (Sultanate of Oman).
Dissertation. University of Berne.
Immen ha user. A. 1996. Cretaceous sediments on the Masi rah
Island Ophiolitc (Sultanate of Oman): Evidence for an unusual bathymetric history. Journal of tire Geological Socierv. London, 153: 539-551.
lmmenhauser, /\ .. Gnos, E. & Peters. Tj. 1997. Late Cretaceous/
Early Tertiary convergence between the Indian and Arahian plates recorded in ophiolites and related sediments.
Tectonopltvsics, 271: 1-19.
de Kaenel, E. & Bergen. J./\. 1993. New Early and Middle
Jurassic coccolith taxa and biostratigraphy from the eastern proto-Atlantic (Morocco. Portugal and DSDP Site
5478). Eclogae Geologicae Ilelvetiae, 86(3): 861-907.
de Kacncl, E .. 11crgcn. J./\. & von Salis Perch-Nielsen, K. 1996.
Jurassic calcareous nannofossils stratigraphy of western
Europe: Compilation of recent studies and calibration of
biocvents. Bulletin de In Sociele Geologique de Fra11ce,
1996.167(1) 15-28
Kristan-Tollmann. E. 1988. Coccolithen aus den ii.lteren
Allgauschichtcn (Alpincr Lias, Sincmur) von Timor. Indonesian. Geo!. Paliio11tol. Mill. /1111sbr11ck, 15: 71-83.
Lauer, G. 1974. Evoluiionary trends in the Arkhangelskicllaceae(calcareous nannoplankton) of the Upper Cretaceous of_Central Oman. SE /\rabia . ..J.rclrives de Science, Geneve,28(2): 259-262
Marquer. D .. Peters. Tj. & Gnos, E. 1995. A new structuralinterpretation for the emplacement of the Masirah
Ophiolitcs (Oman): /\ main Paleocene intra-oceanic thrust.
Geody11anricn;lc1a.8: l:>-19.
Noel. D. 1973. Nannofossilcs calcaircs de sediments jurassiqucs
finemcnt !amines. B11/le1i11 de la :\luseum Na1io11al
d 'flisroire Na111relle. 3e serie, 75: 95-155.
l'crch-Niclscn, K. 1985. Mesozoic calcareous nannofossils. /11:
H.M. Bolli, J.13. Saunders & K Perch-Nielsen (Eds). Plank1011 S1ra1igr11plry: 329-426. Cambridge University Press.
Peters. Tj. (coord.). lmmenhauser, /\., Mcrcolli, I. & Meyer, J.
1995. Geological map
Masirah North and Masirah South
with explanatory notes. Shed K768-North and Sheet K768South, Scale l:50 000. Directorate General of Minerals.
Oman Ministry of Petroleum and Minerals.
Plummer. P.S. & 13clle. E.R. 1995. Mesozoic tectonostratigraphic evolution of the Seychelles micro-continent.
Sedinre11/11ry Geologv, 96: 73-91.
Ricou, L.-E. 1994. Tethys reconstructed: Plates, Continental
fragments and their Boundaries since 260Ma from central
America to Southeast /\sia. Ceody11amica Acla. 7: 169-218.
Salman, G. & Abdulah, I. 1995. Development of the Mozambique and Ruvuma sedimentary basins, offshore Mozambique. Sedime11/ary Geology, 96: 7-41.
Sissingh, W. 1977. Biostratigraphy of Cretaceous calcareous
nannoplankton. Geologie e11 A,/ij11bouw, 56: 37-65.

or99

Journal of Nannoplankton Research, 19, 2, 1997.

K. von Salis & A. fmmenhauser: Mesozoic Nannofossils from Oman .... , p. 95-101.

PLATE 1

Figs 1, 2: Coccoliths or inorganic calcite grains? Sample 1-620 of Middle Triassic age based on radiolaria (Dumitrica

et al., 1997). Magnifications: x7000 & x 11350.
Fig.3: Mitrolithus? SJ> •. Sample I-243. Pliensbachian. x7000.
Fig.4: Biscutum profundum de Kaenel & Bergen ( 1993). Sample 1-24 l, Plicnsbachian. x5000.
Fig.5: Simi/iscutum cruciulus de Kaenel & Bergen ( 1993). Sample 1-24 l, Pliensbachian, x6000.
Fig.6: Simi/iscutum avltum de Kaencl & Bergen (l 993). Sample l-243, Pliensbachian. x8000.
Fig. 7: Lithraphldltes carniolensis Dcflandre ( 1963). Sample 1-356, Upper Maastrichtian, x5000.
Fig.8: Lithastrinus gri/lii? Stradner ( l 962). Sample 1-257, Coniacian/Santonian, x7600.
Fig.9: Micula swastica Stradner & Steinmetz ( I 984 ). Sample 1-356. Upper Maastrichtian. x6300.
Fig.10: Helicolithus trabeculatus (Gorka, 1957) Verbcek ( 1977). Sample 1-26 l, ±Coniacian/Santonian, x6000.
Fig.11: Marthasterites furcatus (Deflandre in Deflandre & Fert. I 954) Dcflandre I 959. Sample I-257, ±Coniacian/Santonian, x6250.
Fig.12: Prediscosphaera cretacea (Arkhangelsky, 1912) Gartner ( 1968). Sample I-261, ±Coniacian/Santonian, x6500.

100

K. von Salis & A. lmmenhauser: Mesozoic Nannofossils from Oman .... , p. 95-101.

Journal of Nannoplankton Research, 19, 2, 1997.

PLATE 1

Mitrolithus? sp.

Coccolith?

Coccolith?

Biscutum profundum

Similiscutum cruciu/us Similiscutum avitum

Lithraphidites carniolensis Lithastrinus grillii (?) Micula swastica

Helicolithus trabeculatus Marthasterites furcatus Prediscosphaera
cretacea=============== 101